REAPPRAISAL OF THE USE OF PARASITES FOR FISH STOCK IDENTIFICATION

Analysis of the geographical distributions of parasites is an excellent source of information about the movement of host fish. Occasionally such analysis can also allow us to discriminate between fish populations, though unequivocal discrimination usually requires methods with a genetic basis. In assessing fish movement, parasites have two advantages over conventional tags: they can more readily detect mass migration and, because the fish only have to be caught once, the data are usually cheaper to obtain. The most important criterion in selecting a parasite to be used as a tag is its longevity in the fish; short-lived parasites give information on short-term movements of the fish, long-lived parasites on more extensive migrations.